most of my decks run 16 or so creatures and 22 land if they are aggro based, if they are control, more like... 4-8 creatures and 26 land.

it really depends on how you want to play, if you want giant green creatures attacking the enemy, then your going to want decent ammount of mana sources, few ramp cards (Search for land) And... big mean creatures you can throw at your enemies' faces.

-None

"The Humans say, If you build it they will come. Alas each time I build something, Most people tend to Run." -Musing of the Dreadboss.

I do a 20/20/20. 20 creatures, 20 land, 20 enchnt, instant, sorcery, and so one ( whatever i missed insert there ) that's usually what i go by, but that's usually a lower costing deck, I'd put a bit more land in and remove some creatures for higher costing goodies. But green is such a good one for pumping out mana quick.

one way to really build a deck is to tell yourself that you are never going to restrict any possibilities.

When I first started out I told myself that I only wanted to play black. That in the end was a huge mistake because now I really like red/blue and missed out on a lot of good cards in those colors that I traded away due to my restrictions.

On to deck building. What you need to do to start out is have an idea. Inside that idea you need to find out what your win conditions are. If you are going to kill with creatures think of your aggro strategy and which creatures you think will do the killing. If its spells put in your spells that you want to win the game with and everything you need to protect those spells or yourself until you can cast them.

As for putting in lands normally mono colored decks you want 20-22 lands since each of your lands will be in the color you need. If you are going multiple colors boost that to about 24-26 lands. One thing I really like to do is build my deck and once it is assembled take about 30 minutes or so of just shuffling and drawing 7 cards. You will find if you are hitting what you want in your opening hand more often then not. If you find your hands are always filled with land or ways to get lands and less of your spells/creatures then remove 1 land at a time and add a spell. If you are always spell flooded remove one of your less important spells and add in land, rinse and repeat.

Next thing is trading. If you are going to start trading I would recommend 1 thing and that's know the value of your cards you want to get rid of and the value of the cards you want. Also don't let people pressure you into trading for cards you don't know if you want even if they make it sound too good to pass up.